1. Field of the Invention
This invention relates to a system for providing high brightness, high contrast image sources that consume minimal electrical power, and that include a holographic information storage plate and a holographic projection screen. The storage plate diffracts at least 70% and preferably at least 80% of incident light, and directs the diffracted light toward predetermined, desired areas on the holographic screen character plate. At the holographic screen character plate, the incident light from the information storage plate is diffused and directed entirely into the viewer's line of sight for optimum brightness.
2. Description of Related Art
Optical holographic data storage provides a high density fixed data base. One such system involves the storage and retrieval of data from a Fourier transform transmission hologram. Such a system uses a lens arrangement for data retrieval and requires considerable space. The use of a transmission hologram in a Fourier transform data system precludes the use of a double-sided holographic memory plate.
Another conventional holographic data storage system increases storage capacity by recording multiple holograms at different polarizations. In such a system, the retrieval or playback is at different polarization angles. Such a system is complex and bulky.
Another prior optical data storage system is commonly called the "optical disc." In such a system, the data is stored in binary form as a series of small holes. The presence of a hole is equivalent to a one state, and the absence of a hole is equivalent to a zero state. The hole is very small, on the order of one to two micrometers. During the retrieval process, the disc is rotated at high speed. The distance between the disc and detecting head is very small, typically two to ten micrometers. The disc can store a large amount of data, but accurate playback is susceptible to vibration and movement. The optical disc system is not usable in a vibrating environment such as a vehicle.
None of these systems is sufficiently rugged, resistant to vibration, high in contrast, and low in power consumption to be of practical use where high-density, small size, short data access time requirements and severe environmental conditions exist, as in aircraft, space, automobile and other uses.